An InDesign 6 file has reverted to a really old version even though it has been saved numerous times over the period during which we have been working on it. We have a pdf of the file when it was last saved on Saturday morning, yet the InDesign file shows it last being worked on a week ago. Our back-up InDesign file on our external back-up drive also shows it as a week old.
Did you try the Open Recent menu? Are you certain it wasn't inadvertently saved in a new location?
This is a duplicate post from one hour ago.